Nowadays, lots of countries around the world have widely used techniques of optical fibers as main transmission tools in network systems. Since optical fiber transmissions are implemented based on total reflection of light, optical fibers have the characteristics of high-speed transmission and low transmission loss. When optical fibers are used as the transmission medium in a network system, the optical fibers have the characteristics of wide bandwidth, high-capacity and high-speed.
Currently, due to the increasing amount of data transmission and user demands for high-speed internet transmission, the amount of data transmission provided by optical fibers is insufficient. In order to overcome the problem of insufficient amount for data transmission, both receipt and transmission at two opposite ends of optical fibers become quite important in addition to the improvement of transmission speed optical fibers. In general, transceiver optical subassemblies located at two ends of an optical fiber are usually equipped with a wavelength division multiplexer or a wavelength division de-multiplexer. The wavelength division multiplexer is capable of simultaneously transmitting a plurality of optical signals having wavelengths different from one another by coupling the plurality of optical signals into a single optical fiber, so as to increase the flow of data transmission in the optical communications network. The wavelength division de-multiplexer, meanwhile, is capable of integrating a set of signals, including a plurality of optical signals having wavelengths different from one another into a plurality of optical signals each having a specific wavelength, and further couples each of the plurality of optical signals into a specific optical channel.
Conventionally, a wavelength division multiplexer or a wavelength division de-multiplexer is disposed in a housing of an optical communication sub-assembly. However, with the trend of miniaturization of various electronic devices, the optical communication sub-assembly is also required to be downsized. Since it is necessary for the optical fibers to be disposed in a much limited space so as to be routed to the input terminal and the output terminal of the wavelength division multiplexer or the wavelength division de-multiplexer, the likelihood for the optical fibers to be damaged during the assembling process increases and bent portions of the optical fibers would lead to loss of optical signal transmission power. Therefore, how to maintain miniaturization of the optical communication sub-assembly and improve the routing of the optical fiber at the same time has become one of the issues to be addressed.